This work was supported by a research grant MOP 119271 to JMW by the Canadian Institute of Health Research. The authors would like to thank Ms. Yao Fang Tan for her outstanding technical assistance.

NOTE: All animal procedures conformed to the animal health and welfare guidelines of the Department of Comparative Medicine at the University of Toronto.
1. Preparation of Hippocampal Slices
<ol>
	<li>Sterilize the following instruments using the dry autoclave at 125 &#176;C: Scalpel handle (#3) (2), Standard pattern forceps, large (1), Small dissector scissor (angled to side) (1), Micro spoon (spoon and flat spatula ends) (1), Micro-spatulas (rounded and rounded tapered ends) (2), Fine paintbrush (1), Fire polished Pasteur pipette (2), Gauze squares, 2 x 2 inches (5).</li>
	<li>When sterile, put the instruments into a sterile container and keep covered until use. Immediately before dissection, immerse instruments in a 70% ethanol solution.</li>
	<li>Prepare a 6-well culture plate with culture insert before beginning the dissection procedure by adding 1 ml of culture medium/well and storing the plate in the incubator at 35 &#176;C and 5% CO2.</li>
</ol>
2. Arrange Dissection Tools in Sterile Laminar Flow hood
<ol>
	<li>Spray the laminar flow hood with 70% ethanol and remove sterilized dissection instruments from alcohol. Allow the instruments to dry while resting on a sterile Petri dish to avoid contact between the alcohol and the dissected brain tissue.</li>
	<li>Deposit 5-7 ml of sterilized ice-cold dissecting solution in 2 large sterile Petri dishes. One dish will chill and clean the head (dirty), the other one for cooling and rinsing the scooped out brain (clean). Place a sterilized filter paper in one of the Petri dish lids for dissecting out the brain.</li>
	<li>Place a small, sterilized filter paper in one of the small Petri dish lid for dissecting out the hippocampus. Deposit 3-5 ml of sterilized ice-cold dissecting solution in 2 small, sterile Petri dishes. One dish will hold the scooped out hippocampus, one will hold sections during separation of hippocampal sections under dissection microscope.</li>
	<li>Prepare the tissue chopper by taping a piece of sterilized filter paper to the cutting stage and mounting a sterile razor blade. Wet the filter paper with sterilized dissecting solution.</li>
	<li>Spray a clean bio-bag with alcohol and place it in laminar flow clean bench.</li>
</ol>
3. Hippocampal Dissection
<ol>
	<li>Spray the P7 Sprague Dawley rat pup with 70% ethanol outside of the laminar flow clean bench and quickly decapitate the animal using large sterile surgical scissors inside the laminar flow bench. Let the head drop into ice-cold dissecting solution in one of the Petri dishes.</li>
	<li>In the Petri dish, rinse off the blood and quickly transfer the head to sterilized filter paper, ventral side down.</li>
	<li>Using the scalpel, cut along the dorsal surface in the sagittal plane to expose the underlying skull. Cut through the skin, but not the underlying bone, which is soft and easily penetrable in rats of this age. Set aside this &#8220;dirty&#8221; scalpel and do not use on brain tissue.</li>
	<li>Using the small dissector scissors (angled to side) and forceps, cut open the skull along sagittal suture of the skull to bregma, the anatomical point on the skull where the coronal suture is intersected perpendicularly by the sagittal suture. Use forceps to pull skull flaps up and away from the midline of the skull.</li>
	<li>Place the micro spoon on the underside of the brain, beneath the brain stem, to gently lift the brain out of the skull. Lift the brain to expose the optic nerves and olfactory bulb on basal surface of brain. Cut these structures with small scissors to fully detach the brain from skull. Remove and transfer the intact brain to the other large Petri dish containing ice-cold dissecting solution.</li>
	<li>Using the micro spoon, transfer the brain to a small Petri-dish lid containing sterile filter paper. With a sterile Pasteur pipette, rinse the brain with a few drops of dissecting solution to keep tissue moist.</li>
	<li>Using a &#8220;clean&#8221; scalpel blade cut the two hemispheres apart. Transfer the left hemisphere back to large Petri dish with micro spoon and place hemisphere pia side down in ice-cold dissecting solution for subsequent use.</li>
	<li>View the medial face of the right hemisphere and identify the edge fornix, a prominent band of white matter along the medial edge of the hippocampus. Using a sterile scalpel, make a sagittal cut through the fornix, but take care because only 0.5 cm of the scalpel tip will be sufficient to cut the fornix.</li>
	<li>Using 2 micro-spatulas, remove the first hippocampus from right hemisphere by placing the right-hand-spatula on the brain stem and lifting the overlying cortex with the left-hand spatula. Gently lift the cortex to reveal the lateral ventricle and medial surface of the hippocampus. A white curved line, the fimbria, should now be visible.</li>
	<li>Align the curvature of spatula with the curvature of the fimbria and gently press the spatula under the fimbria. Slide the spatula left and ride along rostral-caudal axis and then lift spatula in dorsal direction to remove hippocampus.</li>
	<li>Transfer the hippocampus to a 2nd small Petri dish with ice-cold dissecting solution. Repeat the same procedure on the left hemisphere to remove the left hippocampus.</li>
	<li>Using a micro spatula, carefully transfer the hippocampi to the tissue chopper stage. Arrange them adjacent and parallel to each other and perpendicular to the axis of the chopper blade. Use a paintbrush to position the tissue and add a few drops of the dissecting solution on top of the hippocampi.</li>
	<li>Cut the tissue in 400 &#956;m slices without pausing to remove individual slices (usually they will not adhere to the blade). After the whole hippocampus has been cut, use the paintbrush to gently transfer the sections to a 2nd small Petri dish with dissection solution.</li>
	<li>Under a dissecting microscope, carefully separate the floating slices using amicro-spatula and paintbrush.</li>
	<li>Remove the pre-prepared culture plate with culture insert from the incubator and place in a laminar flow hood.</li>
	<li>Using a fire-polished Pasteur pipette, draw 4-5 slices into the pipette and transfer slices to the apical surface of culture insert membrane. Next, adjust the positioning with a paintbrush and leave space between individual sections and the border of the culture insert.</li>
	<li>Using a sterile Pasteur pipette, remove the excess dissecting solution from apical surface of membrane. 
	NOTE: While removing solution avoid drawing tissue sections into the pipette. Alternatively, use a regular pipette (P200 or P1000) with sterilized pipette tips to slowly remove solution.</li>
	<li>Place the culture plate with serum-containing culture medium and the hippocampal slices back into the incubator at 35 &#176;C and 5% CO2. 
	NOTE: If experiment calls for generating cultures from multiple animals, thoroughly clean the laminar flow clean bench between dissections. Return instruments to alcohol solution and replace all Petri-dishes, filter papers and sterile razor blades prior to second dissection.</li>
</ol>
4. Feeding and Maintaining Organotypic Slices
<ol>
	<li>Feed cultures in a sterile laminar flow clean bench.</li>
	<li>Perform the first feeding of the cultured sections 2 days post-dissection. Aspirate old culture medium using sterilized glass pipette.</li>
	<li>Use sterile 5 ml serological pipette to add 1 ml of fresh, sterile, serum-containing medium to the wells.</li>
	<li>Gently replace the culture insert and take care to remove any air bubbles that may have formed underneath membrane surface.</li>
	<li>After the first feeding, change medium every other day.</li>
</ol>
5. Incubating Tissue Slices with Thymidine Analogues to Label Newborn Neurons
<ol>
	<li>In order to study the maturation and integration of dentate granule cells in the hippocampus, incubate the organotypic slices with a thymidine analogue, such as Bromodeoxyuridine (BrdU) or Chlorodeoxyuridine (CldU). Here, we use CldU because of its higher solubility in saline.</li>
	<li>After 3DIV, add 1 &#956;l of 10 mg/ml CldU stock solution in saline to 1 ml of culture medium for a final concentration of 10 &#956;g/ml. If BrdU is used, correct the concentration for differences in molecular weight. Add medium with CldU to culture wells and incubate tissue with CldU-containing medium for 2 hr at 35 &#176;C.</li>
	<li>Following 2 hr of incubation at 35 &#176;C, remove the CldU-containing medium and replace with regular feeding medium to resume normal feeding schedule (outlined above).</li>
</ol>
6. Tissue Fixation and Storage
<ol>
	<li>Establish a timeline for applying treatments and fixing tissue samples before starting culture experiments (Figure 2B).</li>
	<li>At a predetermined day post-dissection, prepare the following in a laboratory fume hood: a 10-50 ml beaker containing 4% paraformaldehyde (PFA) in phosphate buffered saline (PBS); an empty beaker for discarded culture medium; small forceps; and a 1,000 ml pipette with disposable tips.</li>
	<li>Remove the culture plate(s) from incubation chamber and transfer to a fume hood. Tilt the individual well plate inserts with forceps. Next, use a pipette to remove culture medium and transfer to a disposal beaker. Tilt the culture plate at an angle to help ensure that all culture medium is removed.</li>
	<li>Finish removing medium for one culture plate at a time. When medium has been removed, add 1 ml of 4% PFA to each culture well and seal well plate with parafilm. Repeat for as many culture plates as necessary and transfer plates to refrigerator at 4 &#176;C for 24 hr.</li>
	<li>After 24 hr, prepare the following in a fume hood: 10-50 ml beaker containing 0.1% Sodium Azide in PBS; an empty beaker for discarded PFA (follow safety precautions when discarding toxic substances); small forceps; and 1,000 ml pipette with disposable tips.</li>
	<li>Follow the procedure outlined in 6.4 for adding PFA, but add 1 ml of PBS with sodium azide instead. Once completely transferred, seal well plates for future use by wrapping edges in parafilm and storing in refrigerator at 4 &#176;C.</li>
</ol>
7. Sectioning Tissue for Immunohistochemistry
<ol>
	<li>Perform tissue sectioning using a vibratome. The following series of steps help maximize the yield of usable tissue sections from organotypic cultures. 
	NOTE: Immediately following hippocampal dissection and plating of slices, the tissue has a thickness of approximately 400 &#956;m. However, after 2-3 weeks in the incubation chamber, tissue slices will begin to flatten, resulting in a final section thickness of 150-300 &#956;m.</li>
	<li>Prepare the following items to section cultured tissue: a #11 scalpel blade and handle, a glass Petri dish containing ice cold PBS, a micro-dissection forceps, and a clean vibratome cutting stage to mount tissue.</li>
	<li>Use a scalpel to carefully cut along the perimeter of the circular insert membrane so that it can be detached from the plastic insert housing. Leave ample space between the cultured slice and the scalpel.</li>
	<li>Transfer the detached insert membrane to a Petri dish containing PBS. After rinsing in PBS, use forceps to transfer the membrane to the vibratome mounting stage.</li>
	<li>Next, use the scalpel to eliminate excess membrane surrounding cultured slices and cut away excess material to create clean edges. This step will ensure the membrane is flat and can easily adhere to the cutting surface.</li>
	<li>Place 1-2 drops of adhesive on the vibratome cutting stage and spread in even layer using a 22 G needle. Spread adhesive into a rectangular shape with the long edge parallel to the cutting blade of the vibratome. Perform this step quickly, to prevent the adhesive from drying.</li>
	<li>Use forceps to transfer the trimmed membrane containing hippocampal slices to the cutting stage and gently position the membrane on glue and ensure that there are no air bubbles.</li>
	<li>As the superglue dries, transfer the vibratome stage with the glued membrane back to the PBS containing Petri dish. Prepare the vibratome blade and a 48 well plate containing sodium azide to store tissue sections.</li>
	<li>Use the vibratome to generate 30 &#956;m sections of the organotypic slice tissue and transfer to a 48 well plate containing sodium azide for storage and subsequent immunohistochemical staining.</li>
	<li>Refer to pre-existing protocols for immunohistochemical staining26,29.</li>
</ol>

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Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+and+postnatal+injections+of+bromodeoxyuridine+produce+age-dependent+morphological+and+behavioral+abnormalities.">Embryonic and postnatal injections of bromodeoxyuridine produce age-dependent morphological and behavioral abnormalities.</a> The Journal Of Neuroscience : The Official Journal Of The Society For Neuroscience. 19 (6), 2337-2346 (1999).</li><li>Morris, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetic+toxicology+of+5-bromodeoxyuridine+in+mammalian+cells.">The genetic toxicology of 5-bromodeoxyuridine in mammalian cells.</a> Mutation Research. 258 (2), 161-188 (1991).</li><li>Bannigan, J., Langman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+cellular+effect+of+5-bromodeoxyuridine+on+the+mammalian+embryo.">The cellular effect of 5-bromodeoxyuridine on the mammalian embryo.</a> Journal Of Embryology And Experimental Morphology. 50, 123-135 (1979).</li><li>Breunig, J. J., Arellano, J. I., Macklis, J. D., Rakic, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Everything+that+glitters+isn't+gold:+a+critical+review+of+postnatal+neural+precursor+analyses.">Everything that glitters isn't gold: a critical review of postnatal neural precursor analyses.</a> Cell Stem Cell. 1 (6), 612-627 (2007).</li><li>Duque, A., Rakic, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Different+effects+of+bromodeoxyuridine+and+[3H]thymidine+incorporation+into+DNA+on+cell+proliferation,+position,+and+fate.">Different effects of bromodeoxyuridine and [3H]thymidine incorporation into DNA on cell proliferation, position, and fate.</a> The Journal Of Neuroscience : The Official Journal Of The Society For Neuroscience. 31 (42), 15205-15217 (2011).</li><li>Namba, T., Mochizuki, H., Onodera, M., Namiki, H., Seki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postnatal+neurogenesis+in+hippocampal+slice+cultures:+early+in+vitro+labeling+of+neural+precursor+cells+leads+to+efficient+neuronal+production.">Postnatal neurogenesis in hippocampal slice cultures: early in vitro labeling of neural precursor cells leads to efficient neuronal production.</a> Journal of Neuroscience Research. 85 (8), 1704-1712 (2007).</li></ol>

The authors declare that they have no competing financial interests.

Following CldU (or BrdU) administration, the timeline of application of pharmacological agents can be chosen to target newborn DGCs during particular developmental windows. For example, a hypothetical agent can be applied during the second week post-CldU injection, which is proposed to coincide with the age of immature neurons that are at a developmental stage where GABA is depolarizing. Future studies using this protocol could adapt the pharmacological agent and the window of exposure to &#8220;tailor&#8221; the approac...

Adult neurogenesis in the mammalian hippocampus represents a remarkable example of the brain&#8217;s innate capacity for adaptability and plasticity. Dentate granule cells (DGCs) are generated from a renewable pool of neural progenitor cells in the hippocampal dentate gyrus, which is one of the two presently well-characterized neurogenic regions in the mammalian brain, and is thought to be particularly important for learning and memory. The hippocampus is part of the limbic system and has a deep location within the mammalian brain, which makes it a difficult target for precise pharmacological manipulation. Additionally, aberrant neurogenesis has been implicated in conditions, such as epilepsy, schizophrenia, and Alzheimer&#8217;s disease, which has prompted interest in understanding the influence of various pharmacological agents during the maturation and survival of newborn neurons. The distinction between postnatal and adult neurogenesis is blurred and previous studies have shown that many features of in vivo neuronal development in the early postnatal period and adulthood are similar25. Here we emphasize postnatal neurogenesis and suggest possible applications to adult neurogenesis.
Organotypic slice cultures provide an efficient in vitro method for studying various physiological properties of the mammalian hippocampus. The value of slice cultures prepared from rodent brains can be summarized in three main qualities: 1) the protocol is straightforward and requires readily available materials; 2) slice cultures allow for pharmacological studies that eliminate complex variables such as the deep anatomic location of the hippocampus and circumvents the blood brain barrier1; and 3) the well characterized structure of the hippocampus and tri-synaptic circuit is preserved2. Previous investigators have used the organotypic hippocampal culture to study synaptic development and physiology3,4, gliogenesis5-7, ischemic brain damage8,9, neuroprotection and neurorepair10-12 as well as epilepsy13-15.The slice cultures could also provide a useful model system allowing for the monitoring of cell development in conjunction with labeling of cells with green fluorescent protein (GFP) or other vital markers.
Slice cultures have also been previously employed to study postnatal hippocampal neurogenesis16-19, but one important factor in the majority of these studies is the well-characterized degeneration that results from explanting tissue from adult animals after approximately 2 weeks in vitro20,21. For this reason, slice cultures are typically prepared from early post-natal (P5-P10) mice or rat pups, which utilizes the improved viability of early postnatal brain tissue for culturing22. While previous studies have shown that the early postnatal and adult hippocampus differ with regards to synaptic physiology and the expression of specific neuronal subtypes23,24, there is substantial conservation of the choreographed developmental program that newborn dentate granule cells proceed through during maturation25. Additionally, recent studies have suggested that the physiological characteristics of newborn DGCs in culture are very similar to immature neurons in the acute hippocampal slice preparation16.

<table><tbody><tr><td>5-chloro-2&#039;-deoxyuridine (CldU)</td><td>MP Biomedicals</td><td>105478</td><td>Hazardous, Carcinogenic</td></tr><tr><td>Cell culture inserts, 30 mm diameter, 0.4 &amp;micro;m pore size</td><td>Thermo scientific&amp;nbsp;</td><td>140660</td><td>Nuclon delta coating on these inserts provides better tissue adhesion and improves slice quality.</td></tr><tr><td>Conical Centrifuge tubes (sterile)</td><td>Fisher Scientific</td><td>14-432-22</td><td></td></tr><tr><td>Dissector scissors (angled to side)</td><td>Fine Science Tools&amp;nbsp;</td><td>14082-09</td><td></td></tr><tr><td>Minimum essential medium (MEM)</td><td>Gibco</td><td>11095; liquid</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Eclipse Ni-U fluorescent microscope</td><td>Nikon</td><td></td><td></td></tr><tr><td>Glue for tissue</td><td>Krazy Glue</td><td>KG585</td><td>Use minimum amount of glue to achieve adhesion as any tissue exposed to glue will be unusable for IHC.</td></tr><tr><td>Hank&amp;rsquo;s Balanced Salt Solution (HBSS) (500 ml)</td><td>Gibco</td><td>14025-092</td><td>Store at 4 &amp;deg;C</td></tr><tr><td>Horse Serum Heat Inactivated (500 ml)</td><td>Gibco</td><td>16050-122</td><td>Make 50 ml aliquots and store at -20 &amp;deg;C</td></tr><tr><td>Kimwipes</td><td>Kimberly-Clarke</td><td>TW 31KYPBX</td><td></td></tr><tr><td>Modified glass pipettes (bottom of Pasteur pipette removed and edge smoothed with Bunsen flame)</td><td></td><td></td><td></td></tr><tr><td>Petri Dish (100 mm x 15 mm) and (60 mm x 15 mm)</td><td>Fisher Brand</td><td>FB0875712 and FB0875713A</td><td></td></tr><tr><td>Scalpel blades #11</td><td>Fine Science Tools</td><td>10011-00</td><td></td></tr><tr><td>Scalpel handle #3</td><td>Fine Science Tools</td><td>10003-12</td><td></td></tr><tr><td>Serological Pipettes</td><td>Sorfa Medical Plastic Co.</td><td>P8050</td><td></td></tr><tr><td>Standard Pattern forceps</td><td>Fine Science Tools</td><td>11000-12</td><td></td></tr><tr><td>Sterile vacuum filter</td><td>Thermo-Scientific</td><td>565-0020</td><td></td></tr><tr><td>Surgical Scissors</td><td>Fine Science Tools</td><td>14054-13</td><td></td></tr><tr><td>Syringe driven filter unit</td><td>Millipore-Millex</td><td>SLGP033RS</td><td></td></tr><tr><td>Tissue chopper with moveable stage</td><td>Stoelting&amp;nbsp;</td><td>51425</td><td></td></tr><tr><td>Fine tip paintbrush</td><td></td><td></td><td></td></tr></tbody></table>

organotypic slice cultures for studies of postnatal neurogenesis

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This method maintains the characteristic topographical morphology of the hippocampus while allowing direct application of pharmacological agents to the developing hippocampal dentate gyrus. Additionally, slice cultures can be maintained for up to 4 weeks and thus, allow one to study the maturation process of newborn granule neurons. Slice cultures allow for efficient pharmacological manipulation of hippocampal slices while excluding complex variables such as uncertainties related to the deep anatomic location of the hippocampus as well as the blood brain barrier. For these reasons, we sought to optimize organotypic slice cultures specifically for postnatal neurogenesis research.

Determining if organotypic cultures would be suitable for adult neurogenesis research required that they satisfy two main criteria: 1) that slices maintain characteristic morphological features of hippocampal slices after 10-21 days in vitro (DIV), and 2) that newborn DGCs can be quantified using standard immunohistochemical techniques commonly employed in adult neurogenesis research. Regarding the first criterion, Figure 1A and 1B highlight the preserved hippocampal morphology....

Watch this Scientific Journal Video about Organotypic Slice Cultures for Studies of Postnatal Neurogenesis at JoVE.com

Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

Here we describe a technique for studying hippocampal postnatal neurogenesis using the organotypic slice culture technique. This method allows for in vitro manipulation of adult neurogenesis and allows for the direct application of pharmacological agents to the cultured hippocampus.

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This ...

organotypic-slice-cultures-for-studies-of-postnatal-neurogenesis

Research

JoVE Journal

Developmental Biology

12.3K Views.  University of Toronto.  Hier beschrijven we een techniek voor het bestuderen van de hippocampus postnatale neurogenese met de organotypische slice cultuur techniek. Deze werkwijze maakt in vitro manipulatie van volwassen neurogenese en maakt de directe toepassing van farmacologische middelen aan de gekweekte hippocampus. 

Video: Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

Organotypic Slice Culture of E18 Rat Brains

Organotypic slice cultures from embryonic rodent brains are widely used to study brain development. While there are often advantages to an in-vivo system, organotypic slice cultures allow one to perform a number of manipulations that are not presently feasible in-vivo. To date, organtotypic embryonic brain slice cultures have been used to follow individual cells using time-lapse microscopy, manipulate the expression of genes in the ganglionic emanances (a region that is hard to target by in-utero electroporation), as well as for pharmacological studies. In this video protocol we demonstrate how to make organotypic slice cultures from rat embryonic day 18 embryos. The protocol involves dissecting the embryos, embedding them on ice in low melt agarose, slicing the embedded brains on the vibratome, and finally plating the slices onto filters in culture dishes. This protocol is also applicable in its present form to making organotypic slice cultures from different embryonic ages for both rats and mice. 

Organotypic slice cultures from embryonic rodent brains are widely used to study brain development. While there are often advantages to an in-vivo system, ...

Biology

Organotypic Slice Culture of GFP-expressing Mouse Embryos for Real-time Imaging of Peripheral Nerve Outgrowth

For many purposes, the cultivation of mouse embryos ex vivo as organotypic slices is desirable. For example, we employ a transgenic mouse line (tauGFP) in which the enhanced version of the green fluorescent protein (EGFP) is exclusively expressed in all neurons of the developing central and peripheral nervous system1, allowing the possibility to both film the innervation of the forelimb and to manipulate this process with pharmacological and genetic techniques2. The most critical parameter in the successful cultivation of such slice cultures is the method by which the slices are prepared. After extensive testing of a variety of methods, we have found that a vibratome is the best possible device to slice the embryos such that they routinely result in a culture that demonstrates viability over a period of several days, and most importantly, develops in an age-specific manner. For mid-gestation embryos, this includes the normal outgrowth of spinal nerves from the spinal cord and the dorsal root ganglia to their targets in the periphery and the proper determination of skeletal and muscle tissue. 
In this work, we present a method for processing whole embryos of embryonic day (E) E10 to E12 into 300 - 400 micrometer slices for cultivation in a standard tissue culture incubator, which can be studied for up to two days after slice preparation. Critical for the success of this approach is the use of a vibratome to slice each agarose-embedded embryo. This is followed by the cultivation of the slices upon Millicell culture membrane inserts placed upon a small volume of medium, resulting in an interface culture technique. One litter with an average of 7 embryos routinely produces at least 14 slices (2-3 slices of the forelimb region per embryo), which varies slightly due to the age of the embryos as well as to the thickness of the slices. About 80% of the cultured slices show nerve outgrowth, which can be measured througout the culturing period2. Representative results using the tauGFP mouse line are demonstrated.

We present a method to prepare organotypic slices of mid-gestation mouse embryos for the cultivation and time-lapse imaging of peripheral nerve outgrowth.

For many purposes, the cultivation of mouse embryos ex vivo as organotypic slices is desirable. For example, we employ a transgenic mouse line (tauGFP) in ...

Neuroscience

Organotypic Hippocampal Slice Cultures

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the strength of their connections after brief periods of strong activation. This phenomenon, known as long-term potentiation (LTP) can last for hours or days and has become the best candidate mechanism for learning and memory 2. In addition, the well defined anatomy and connectivity of the hippocampus 3 has made it a classical model system to study synaptic transmission and synaptic plasticity4.
As our understanding of the physiology of hippocampal synapses grew and molecular players became identified, a need to manipulate synaptic proteins became imperative. Organotypic hippocampal cultures offer the possibility for easy gene manipulation and precise pharmacological intervention but maintain synaptic organization that is critical to understanding synapse function in a more naturalistic context than routine culture dissociated neurons methods.
Here we present a method to prepare and culture hippocampal slices that can be easily adapted to other brain regions. This method allows easy access to the slices for genetic manipulation using different approaches like viral infection 5,6 or biolistics 7. In addition, slices can be easily recovered for biochemical assays 8, or transferred to microscopes for imaging 9 or electrophysiological experiments 10.

We describe a method to prepare organotypic hippocampal slices that can be easily adapted to other brain regions. Brain slices are laid on porous membranes and culture media is allowed to form an interface. This method preserves the gross architecture of the hippocampus for up to 2 weeks in culture.

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the ...

An Organotypic Slice Assay for High-Resolution Time-Lapse Imaging of Neuronal Migration in the Postnatal Brain

Neurogenesis in the postnatal brain depends on maintenance of three biological events: proliferation of progenitor cells, migration of neuroblasts, as well as differentiation and integration of new neurons into existing neural circuits. For postnatal neurogenesis in the olfactory bulbs, these events are segregated within three anatomically distinct domains: proliferation largely occurs in the subependymal zone (SEZ) of the lateral ventricles, migrating neuroblasts traverse through the rostral migratory stream (RMS), and new neurons differentiate and integrate within the olfactory bulbs (OB). The three domains serve as ideal platforms to study the cellular, molecular, and physiological mechanisms that regulate each of the biological events distinctly. This paper describes an organotypic slice assay optimized for postnatal brain tissue, in which the extracellular conditions closely mimic the in vivo environment for migrating neuroblasts. We show that our assay provides for uniform, oriented, and speedy movement of neuroblasts within the RMS. This assay will be highly suitable for the study of cell autonomous and non-autonomous regulation of neuronal migration by utilizing cross-transplantation approaches from mice on different genetic backgrounds.

This protocol describes an organotypic slice assay optimized for the postnatal brain and high-resolution time-lapse imaging of neuroblast migration in the rostral migratory stream.

Neurogenesis in the postnatal brain depends on maintenance of three biological events: proliferation of progenitor cells, migration of neuroblasts, as ...

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

The mouse is an excellent model organism to study mammalian brain development due to the abundance of molecular and genetic data. However, the developing mouse brain is not suitable for easy manipulation and imaging in vivo since the mouse embryo is inaccessible and opaque. Organotypic slice cultures of embryonic brains are therefore widely used to study murine brain development in vitro. Ex-vivo manipulation or the use of transgenic mice allows the modification of gene expression so that subpopulations of neuronal or glial cells can be labeled with fluorescent proteins. The behavior of labeled cells can then be observed using time-lapse imaging. Time-lapse imaging has been particularly successful for studying cell behaviors that underlie the development of the cerebral cortex at late embryonic stages 1-2. Embryonic organotypic slice culture systems in brain regions outside of the forebrain are less well established. Therefore, the wealth of time-lapse imaging data describing neuronal cell migration is restricted to the forebrain 3,4. It is still not known, whether the principles discovered for the dorsal brain hold true for ventral brain areas. In the ventral brain, neurons are organized in neuronal clusters rather than layers and they often have to undergo complicated migratory trajectories to reach their final position. The ventral midbrain is not only a good model system for ventral brain development, but also contains neuronal populations such as dopaminergic neurons that are relevant in disease processes. While the function and degeneration of dopaminergic neurons has been investigated in great detail in the adult and ageing brain, little is known about the behavior of these neurons during their differentiation and migration phase 5. We describe here the generation of slice cultures from the embryonic day (E) 12.5 mouse ventral midbrain. These slice cultures are potentially suitable for monitoring dopaminergic neuron development over several days in vitro. We highlight the critical steps in generating brain slices at these early stages of embryonic development and discuss the conditions necessary for maintaining normal development of dopaminergic neurons in vitro. We also present results from time lapse imaging experiments. In these experiments, ventral midbrain precursors (including dopaminergic precursors) and their descendants were labeled in a mosaic manner using a Cre/loxP based inducible fate mapping system 6.

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

A method to generate organotypic slices from the E12.5 murine embryonic midbrain is described. The organotypic slice cultures can be used to observe the behavior of dopaminergic neurons or other ventral midbrain neurons.

The  mouse is an excellent model organism to study mammalian brain development due  to the abundance of molecular and genetic data. However, the ...

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the first born neurons remain closer to the ventricle while the last born neurons migrate past the first born neurons towards the surface of the brain1. In addition to neuronal migration2, a key process for normal cortical function is the regulation of neuronal morphogenesis3. While neuronal morphogenesis can be studied in vitro in primary cultures, there is much to be learned from how these processes are regulated in tissue environments.
We describe techniques to analyze neuronal migration and/or morphogenesis in organotypic slices of the cerebral cortex4,6. A pSilencer modified vector is used which contains both a U6 promoter that drives the double stranded hairpin RNA and a separate expression cassette that encodes GFP protein driven by a CMV promoter7-9. Our approach allows for the rapid assessment of defects in neurite outgrowth upon specific knockdown of candidate genes and has been successfully used in a screen for regulators of neurite outgrowth8. Because only a subset of cells will express the RNAi constructs, the organotypic slices allow for a mosaic analysis of the potential phenotypes. Moreover, because this analysis is done in a near approximation of the in vivo environment, it provides a low cost and rapid alternative to the generation of transgenic or knockout animals for genes of unknown cortical function. Finally, in comparison with in vivo electroporation technology, the success of ex vivo electroporation experiments is not dependant upon proficient surgery skill development and can be performed with a shorter training time and skill.

Methods for Study of Neuronal Morphogenesis: Ex vivo RNAi Electroporation in Embryonic Murine Cerebral Cortex

To conduct a rapid assessment of the function of genes in the development of cerebral cortex, we describe methods involving the ex vivo electroporation of plasmids co-expressing inhibitory RNA (RNAi) and GFP in murine embryonic cortex. This protocol is amenable to the study of various aspects of neurodevelopment such as neurogenesis, neuronal migration and neuronal morphogenesis including dendrite and axon outgrowth.

The cerebral cortex directs higher cognitive functions. This six layered structure is generated in an inside-first, outside-last manner, in which the ...

Organotypic Slice Cultures to Study Oligodendrocyte Dynamics and Myelination

NG2 expressing cells (polydendrocytes, oligodendrocyte precursor cells) are the fourth major glial cell population in the central nervous system. During embryonic and postnatal development they actively proliferate and generate myelinating oligodendrocytes. These cells have commonly been studied in primary dissociated cultures, neuron cocultures, and in fixed tissue. Using newly available transgenic mouse lines slice culture systems can be used to investigate proliferation and differentiation of oligodendrocyte lineage cells in both gray and white matter regions of the forebrain and cerebellum. Slice cultures are prepared from early postnatal mice and are kept in culture for up to 1 month. These slices can be imaged multiple times over the culture period to investigate cellular behavior and interactions. This method allows visualization of NG2 cell division and the steps leading to oligodendrocyte differentiation while enabling detailed analysis of region-dependent NG2 cell and oligodendrocyte functional heterogeneity. This is a powerful technique that can be used to investigate the intrinsic and extrinsic signals influencing these cells over time in a cellular environment that closely resembles that found in vivo.

A technique to study NG2 cells and oligodendrocytes using a slice culture system of the forebrain and cerebellum is described. This method allows examination of the dynamics of proliferation and differentiation of cells within the oligodendrocyte lineage where the extracellular environment can be easily manipulated while maintaining tissue cytoarchitecture.

NG2 expressing cells (polydendrocytes, oligodendrocyte precursor cells) are the fourth major glial cell population in the central nervous system. During ...

Organotypic Hippocampal Slice Cultures As a Model to Study Neuroprotection and Invasiveness of Tumor Cells

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. This model is suitable for addressing different research questions that involve studies on neuroprotection, electrophysiological experiments on neurons, neuronal networks or tumor invasion. The hippocampal architecture and neuronal activity in multisynaptic circuits are well conserved in OHSC, even though the slicing procedure itself initially lesions and leads to formation of a glial scar. The scar formation alters presumably the mechanical properties and diffusive behavior of small molecules, etc. Slices allow the monitoring of time dependent processes after brain injury without animal surgery, and studies on interactions between various brain-derived cell types, namely astrocytes, microglia and neurons under both physiological and pathological conditions. An ambivalent aspect of this model is the absence of blood flow and immune blood cells. During the progression of the neuronal injury, migrating immune cells from the blood play an important role. As those cells are missing in slices, the intrinsic processes in the culture may be observed without external interference. Moreover, in OHSC the composition of the medium-external environment is precisely controlled. A further advantage of this method is the lower number of sacrificed animals compared to standard preparations. Several OHSC can be obtained from one animal making simultaneous studies with multiple treatments in one animal possible. For these reasons, OHSC are well suited to analyze the effects of new protective therapeutics after tissue damage or during tumor invasion. 
The protocol presented here describes a preparation method of OHSC that allows generating highly reproducible, well preserved slices that can be used for a variety of experimental research, like neuroprotection or tumor invasion studies.

Organotypic hippocampal slice cultures (OHSC) represent an in vitro model that simulates the in vivo situation very well. Here we describe a vibratome-based improved slicing protocol to obtain high quality slices for use in assessing the neuroprotective potential of novel substances or the biological behavior of tumor cells.

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. ...

Ex Vivo Oculomotor Slice Culture from Embryonic GFP-Expressing Mice for Time-Lapse Imaging of Oculomotor Nerve Outgrowth

Accurate eye movements are crucial for vision, but the development of the ocular motor system, especially the molecular pathways controlling axon guidance, has not been fully elucidated. This is partly due to technical limitations of traditional axon guidance assays. To identify additional axon guidance cues influencing the oculomotor nerve, an ex vivo slice assay to image the oculomotor nerve in real-time as it grows towards the eye was developed. E10.5 IslMN-GFP embryos are used to generate ex vivo slices by embedding them in agarose, slicing on a vibratome, then growing them in a microscope stage-top incubator with time-lapse photomicroscopy for 24-72 h. Control slices recapitulate the in vivo timing of outgrowth of axons from the nucleus to the orbit. Small molecule inhibitors or recombinant proteins can be added to the culture media to assess the role of different axon guidance pathways. This method has the advantages of maintaining more of the local microenvironment through which axons traverse, not axotomizing the growing axons, and assessing the axons at multiple points along their trajectory. It can also identify effects on specific subsets of axons. For example, inhibition of CXCR4 causes axons still within the midbrain to grow dorsally rather than ventrally, but axons that have already exited ventrally are not affected.

An ex vivo slice assay allows oculomotor nerve outgrowth to be imaged in real time. Slices are generated by embedding E10.5 IslMN:GFP embryos in agarose, slicing on a vibratome, and growing in a stage-top incubator. The role of axon guidance pathways is assessed by adding inhibitors to the culture media.

Accurate eye movements are crucial for vision, but the development of the ocular motor system, especially the molecular pathways controlling axon ...

Purkinje Cell Survival in Organotypic Cerebellar Slice Cultures

Organotypic slice culture is a powerful in vitro model that mimicks in vivo conditions more closely than dissociated primary cell cultures. In early postnatal development, cerebellar Purkinje cells are known to go through a vulnerable period, during which they undergo programmed cell death. Here, we provide a detailed protocol to perform mouse organotypic cerebellar slice culture during this critical time. The slices are further labeled to assess Purkinje cell survival and the efficacy of neuroprotective treatments. This method can be extremely valuable to screen for new neuroactive molecules.

Organotypic slice cultures are a powerful tool to study neurodevelopmental or degenerative/regenerative processes. Here, we describe a protocol that models the neurodevelopmental death of Purkinje cells in mouse cerebellar slice cultures. This method may benefit research in neuroprotective drug discovery.

Organotypic slice culture is a powerful in vitro model that mimicks in vivo conditions more closely than dissociated primary cell cultures. In early ...

Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

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